Dynamic cross-talk mitigation for integrated touch screens

ABSTRACT

A touch input device configured to mitigate the effects of dynamic cross talk noise is provided. The touch input device can dither an effective resistance of a plurality of gate lines proximal to the touch sensor panel in order to determine if a phase of a touch signal demodulator needs to be adjusted.

FIELD OF THE DISCLOSURE

This relates generally to touch sensing, and more particularly, todynamic cross-talk mitigation for integrated display touch screens.

BACKGROUND OF THE DISCLOSURE

Many types of input devices are presently available for performingoperations in a computing system, such as buttons or keys, mice,trackballs, joysticks, touch sensor panels, touch screens and the like.Touch screens, in particular, are becoming increasingly popular becauseof their ease and versatility of operation as well as their decliningprice. Touch screens can include a touch sensor panel, which can be aclear panel with a touch-sensitive surface, and a display device such asa liquid crystal display (LCD) that can be positioned partially or fullybehind the panel so that the touch-sensitive surface can cover at leasta portion of the viewable area of the display device. Touch screens canallow a user to perform various functions by touching the touch sensorpanel using a finger, stylus or other object at a location oftendictated by a user interface (UI) being displayed by the display device.In general, touch screens can recognize a touch and the position of thetouch on the touch sensor panel, and the computing system can theninterpret the touch in accordance with the display appearing at the timeof the touch, and thereafter can perform one or more actions based onthe touch. In the case of some touch sensing systems, a physical touchon the display is not needed to detect a touch. For example, in somecapacitive-type touch sensing systems, fringing fields used to detecttouch can extend beyond the surface of the display, and objectsapproaching near the surface may be detected near the surface withoutactually touching the surface.

Capacitive touch sensor panels can be formed from a matrix of drive andsense lines of a substantially transparent conductive material, such asIndium Tin Oxide (ITO), often arranged in rows and columns in horizontaland vertical directions on a substantially transparent substrate. It isdue in part to their substantial transparency that capacitive touchsensor panels can be overlaid on a display to form a touch screen, asdescribed above. Some touch screens can be formed by integrating touchsensing circuitry into a display node stackup (i.e., the stackedmaterial layers forming the display nodes). This integration of thetouch hardware and display hardware can lead to parasitic capacitancesor “cross-talk” which act as noise and can interfere with normal touchdetection.

SUMMARY

The following description includes examples of reducing or eliminatingthe effects of noise that can be generated by proximal electronics of atouch screen device, such as a gate line voltage system that appliesvoltage to gate lines of the touch screen. In one example, a touchsignal demodulator local oscillator can have its phase tuned such thatthe phase is orthogonal to the phase of a noise signal created byparasitic signal paths. During operation of the device, various circuitparameters can be modulated and the resulting touch signal analyzed, toensure that the demodulator phase remains orthogonal to the noisesignal. If it is found that the demodulator is not tuned to beorthogonal to the noise signal, then the demodulator phase can beadjusted to ensure orthogonality with the noise signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C illustrate an example mobile telephone, an example mediaplayer, and an example personal computer that each include an exampletouch screen according to examples of the disclosure.

FIG. 2 is a block diagram of an example computing system thatillustrates one implementation of an example touch screen according toexamples of the disclosure.

FIG. 3 is a more detailed view of the touch screen of FIG. 2 showing anexample configuration of drive lines and sense lines according toexamples of the disclosure.

FIG. 4 illustrates an example configuration in which touch sensingcircuitry includes common electrodes (Vcom) according to examples of thedisclosure.

FIG. 5 illustrates an exploded view of example display node stackupsaccording to examples of the disclosure.

FIG. 6 illustrates an example touch sensing operation according toexamples of the disclosure.

FIG. 7a illustrates an example touch sensing circuit according toexamples of the disclosure.

FIG. 7b illustrates an example touch sensing circuit with parasiticcapacitance pathways according to examples of the disclosure.

FIG. 8 illustrates an example touch sensing demodulation circuitaccording to examples of the disclosure.

FIGS. 9A-9C illustrate various relationships between the phase of asignal and the phase of a local oscillator according to examples of thedisclosure.

FIGS. 10A-10C illustrate various relationships between the phase of asignal, the phase of a noise signal, and the phase of a local oscillatoraccording to examples of the disclosure.

FIG. 11 illustrates an example method of dynamically adjusting a localoscillator phase according to examples of the disclosure.

FIG. 12 illustrates an example gate line voltage system according toexamples of the disclosure.

FIG. 13 illustrates an example method of dithering the resistance of agate line voltage system.

FIG. 14 illustrates another example method of dithering the resistanceof a gate line voltage system.

FIG. 15 illustrates another example method of dithering the resistanceof a gate lien voltage system.

FIG. 16 illustrates an example frequency response of a detected touchand noise signal according to examples of the disclosure.

FIG. 17 shows an exemplary embodiment of an in-cell touch controllerwith additional features for DTX compensation.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings which form a part hereof, and in which it is shownby way of illustration specific examples of the disclosure that can bepracticed. It is to be understood that other examples can be used andstructural changes can be made without departing from the scope of theexamples of this disclosure.

The following description relates to the dynamic mitigation of noisecause by parasitic capacitances which can act as a noise source to touchdetection. A demodulator of the touch detection circuitry can be tunedto be orthogonal to the phase of a noise signal, thereby cancelling orsubstantially reducing the effect of the noise signal on signal to noiseratio. Periodically throughout operation of the device, the touchdetection system can monitor whether or not the demodulator is stilltuned to be orthogonal to the noise, and if it is determined that it isnot, can adjust the demodulator so that the phase remains orthogonal tothe noise.

As touch sensing circuitry becomes more closely integrated withcircuitry of other systems, undesirable interaction between circuitelements of different systems can be more likely to occur. For example,touch sensing circuitry can be integrated into the display node stackupsof integrated touch screens. Display node stackups are typicallymanufactured by processes including depositing, masking, etching,doping, etc., of materials such as conductive materials (e.g., metal,substantially transparent conductors), semiconductive materials (e.g.,polycrystalline silicon (Poly-Si)), and dielectric materials (e.g.,SiO2, organic materials, SiNx). Various elements formed within a displaynode stackup can operate as circuitry of the display system to generatean image on the display, while other elements can operate as circuitryof a touch sensing system that senses one or more touches on or near thedisplay.

FIGS. 1A-1C show example systems in which a touch screen according toexamples of the disclosure may be implemented. FIG. 1A illustrates anexample mobile telephone 136 that includes a touch screen 124. FIG. 1Billustrates an example digital media player 140 that includes a touchscreen 126. FIG. 1C illustrates an example personal computer 144 thatincludes a touch screen 128. Although not shown in the figures, thepersonal computer 144 can also be a tablet computer or a desktopcomputer with a touch-sensitive display. Touch screens 124, 126, and 128may be based on, for example, self capacitance or mutual capacitance, oranother touch sensing technology. A mutual capacitance based touchsystem can include, for example, drive regions and sense regions, suchas drive lines and sense lines. For example, drive lines can be formedin rows while sense lines can be formed in columns. Touch nodes can beformed at the intersections of the rows and columns. During operation,the rows can be stimulated with an AC waveform and a mutual capacitancecan be formed between the row and the column of the touch node. As anobject approaches the touch node, some of the charge being coupledbetween the row and column of the touch node can instead be coupled ontothe object. This reduction in charge coupling across the touch node canresult in a net decrease in the mutual capacitance between the row andthe column and a reduction in the AC waveform being coupled across thetouch node. This reduction in the charge-coupled AC waveform can bedetected and measured by the touch sensing system to determine thepositions of multiple objects when they touch the touch screen. In someexamples, a touch screen can be multi-touch, single touch, projectionscan, full-imaging multi-touch, or any capacitive touch.

FIG. 2 is a block diagram of an example computing system 200 thatillustrates one implementation of an example touch screen 220 accordingto examples of the disclosure. Computing system 200 could be includedin, for example, mobile telephone 136, digital media player 140,personal computer 144, or any mobile or non-mobile computing device thatincludes a touch screen. Computing system 200 can include a touchsensing system including one or more touch processors 202, peripherals204, a touch controller 206, and touch sensing circuitry (described inmore detail below). Peripherals 204 can include, but are not limited to,random access memory (RAM) or other types of memory or storage, watchdogtimers and the like. Touch controller 206 can include, but is notlimited to, one or more sense channels 208, channel scan logic 210 anddriver logic 214. Channel scan logic 210 can access RAM 212,autonomously read data from the sense channels and provide control forthe sense channels. In addition, channel scan logic 210 can controldriver logic 214 to generate stimulation signals 216 at variousfrequencies and phases that can be selectively applied to drive regionsof the touch sensing circuitry of touch screen 220, as described in moredetail below. In some examples, touch controller 206, touch processor202 and peripherals 204 can be integrated into a single applicationspecific integrated circuit (ASIC).

Computing system 200 can also include a host processor 228 for receivingoutputs from touch processor 202 and performing actions based on theoutputs. For example, host processor 228 can be connected to programstorage 232 and a display controller, such as an LCD driver 234. Hostprocessor 228 can use LCD driver 234 to generate an image on touchscreen 220, such as an image of a user interface (UI), and can use touchprocessor 202 and touch controller 206 to detect a touch on or neartouch screen 220, such a touch input to the displayed UI. The touchinput can be used by computer programs stored in program storage 232 toperform actions that can include, but are not limited to, moving anobject such as a cursor or pointer, scrolling or panning, adjustingcontrol settings, opening a file or document, viewing a menu, making aselection, executing instructions, operating a peripheral deviceconnected to the host device, answering a telephone call, placing atelephone call, terminating a telephone call, changing the volume oraudio settings, storing information related to telephone communicationssuch as addresses, frequently dialed numbers, received calls, missedcalls, logging onto a computer or a computer network, permittingauthorized individuals access to restricted areas of the computer orcomputer network, loading a user profile associated with a user'spreferred arrangement of the computer desktop, permitting access to webcontent, launching a particular program, encrypting or decoding amessage, and/or the like. Host processor 228 can also perform additionalfunctions that may not be related to touch processing.

Touch screen 220 can include touch sensing circuitry that can include acapacitive sensing medium having a plurality of drive lines 222 and aplurality of sense lines 223. It should be noted that the term “lines”is a sometimes used herein to mean simply conductive pathways, as oneskilled in the art will readily understand, and is not limited toelements that are strictly linear, but includes pathways that changedirection, and includes pathways of different size, shape, materials,etc. Drive lines 222 can be driven by stimulation signals 216 fromdriver logic 214 through a drive interface 224, and resulting sensesignals 217 generated in sense lines 223 can be transmitted through asense interface 225 to sense channels 208 (also referred to as an eventdetection and demodulation circuit) in touch controller 206. In thisway, drive lines and sense lines can be part of the touch sensingcircuitry that can interact to form capacitive sensing nodes, which canbe thought of as touch picture elements (touch nodes), such as touchnodes 226 and 227. This way of understanding can be particularly usefulwhen touch screen 220 is viewed as capturing an “image” of touch. Inother words, after touch controller 206 has determined whether a touchhas been detected at each touch node in the touch screen, the pattern oftouch nodes in the touch screen at which a touch occurred can be thoughtof as an “image” of touch (e.g. a pattern of fingers touching the touchscreen).

In some example examples, touch screen 220 can be an integrated touchscreen in which touch sensing circuit elements of the touch sensingsystem can be integrated into the display node stackups of a display. Anexample integrated touch screen in which examples of the disclosure canbe implemented with now be described with reference to FIGS. 3-6. FIG. 3is a more detailed view of touch screen 220 showing an exampleconfiguration of drive lines 222 and sense lines 223 according toexamples of the disclosure. As shown in FIG. 3, each drive line 222 canbe formed of one or more drive line segments 301 that can beelectrically connected by drive line links 303 at connections 305. Driveline links 303 are not electrically connected to sense lines 223,rather, the drive line links can bypass the sense lines through bypasses307. Drive lines 222 and sense lines 223 can interact capacitively toform touch nodes such as touch nodes 226 and 227. Drive lines 222 (i.e.,drive line segments 301 and corresponding drive line links 303) andsense lines 223 can be formed of electrical circuit elements in touchscreen 220. In the example configuration of FIG. 3, each of touch nodes226 and 227 can include a portion of one drive line segment 301, aportion of a sense line 223, and a portion of another drive line segment301. For example, touch node 226 can include a right-half portion 309 ofa drive line segment on one side of a portion 311 of a sense line, and aleft-half portion 313 of a drive line segment on the opposite side ofportion 311 of the sense line.

The circuit elements can include, for example, elements that can existin conventional LCD displays, as described above. It is noted thatcircuit elements are not limited to whole circuit components, such awhole capacitor, a whole transistor, etc., but can include portions ofcircuitry, such as only one of the two plates of a parallel platecapacitor. FIG. 4 illustrates an example configuration in which commonelectrodes (Vcom) can form portions of the touch sensing circuitry of atouch sensing system. Each display node includes a common electrode 401,which is a circuit element of the display system circuitry in the nodestackup (i.e., the stacked material layers forming the display nodes) ofthe display nodes of some types of conventional LCD displays, e.g.,fringe field switching (FFS) displays, that can operate as part of thedisplay system to display an image.

In the example shown in FIG. 4, each common electrode (Vcom) 401 canserve as a multi-function circuit element that can operate as displaycircuitry of the display system of touch screen 220 and can also operateas touch sensing circuitry of the touch sensing system. In this example,each common electrode 401 can operate as a common electrode of thedisplay circuitry of the touch screen, and can also operate togetherwhen grouped with other common electrodes as touch sensing circuitry ofthe touch screen. For example, a group of common electrodes 401 canoperate together as a capacitive part of a drive line or a sense line ofthe touch sensing circuitry during the touch sensing phase. Othercircuit elements of touch screen 220 can form part of the touch sensingcircuitry by, for example, electrically connecting together commonelectrodes 401 of a region, switching electrical connections, etc. Ingeneral, each of the touch sensing circuit elements may be either amulti-function circuit element that can form part of the touch sensingcircuitry and can perform one or more other functions, such as formingpart of the display circuitry, or may be a single-function circuitelement that can operate as touch sensing circuitry only. Similarly,each of the display circuit elements may be either a multi-functioncircuit element that can operate as display circuitry and perform one ormore other functions, such as operating as touch sensing circuitry, ormay be a single-function circuit element that can operate as displaycircuitry only. Therefore, in some examples, some of the circuitelements in the display node stackups can be multi-function circuitelements and other circuit elements may be single-function circuitelements. In other examples, all of the circuit elements of the displaynode stackups may be single-function circuit elements.

In addition, although example examples herein may describe the displaycircuitry as operating during a display phase, and describe the touchsensing circuitry as operating during a touch sensing phase, it shouldbe understood that a display phase and a touch sensing phase may beoperated at the same time, e.g., partially or completely overlap, or thedisplay phase and touch phase may operate at different times. Also,although example examples herein describe certain circuit elements asbeing multi-function and other circuit elements as beingsingle-function, it should be understood that the circuit elements arenot limited to the particular functionality in other examples. In otherwords, a circuit element that is described in one example herein as asingle-function circuit element may be configured as a multi-functioncircuit element in other examples, and vice versa.

For example, FIG. 4 shows common electrodes 401 grouped together to formdrive region segments 403 and sense regions 405 that generallycorrespond to drive line segments 301 and sense lines 223, respectively.Grouping multi-function circuit elements of display nodes into a regioncan mean operating the multi-function circuit elements of the displaynodes together to perform a common function of the region. Grouping intofunctional regions may be accomplished through one or a combination ofapproaches, for example, the structural configuration of the system(e.g., physical breaks and bypasses, voltage line configurations), theoperational configuration of the system (e.g., switching circuitelements on/off, changing voltage levels and/or signals on voltagelines), etc.

Multi-function circuit elements of display nodes of the touch screen canoperate in both the display phase and the touch phase. For example,during a touch phase, common electrodes 401 can be grouped together toform touch signal lines, such as drive regions and sense regions. Insome examples circuit elements can be grouped to form a continuous touchsignal line of one type and a segmented touch signal line of anothertype. For example, FIG. 4 shows one example in which drive regionsegments 403 and sense regions 405 correspond to drive line segments 301and sense lines 223 of touch screen 220. Other configurations arepossible in other examples; for example, common electrodes 401 could begrouped together such that drive lines are each formed of a continuousdrive region and sense lines are each formed of a plurality of senseregion segments linked together through connections that bypass a driveregion.

The drive regions in the example of FIG. 3 are shown in FIG. 4 asrectangular regions including a plurality of common electrodes ofdisplay nodes, and the sense regions of FIG. 3 are shown in FIG. 4 asrectangular regions including a plurality of common electrodes ofdisplay nodes extending the vertical length of the LCD. In someexamples, a touch node of the configuration of FIG. 4 can include, forexample, a 64×64 area of display nodes. However, the drive and senseregions are not limited to the shapes, orientations, and positionsshown, but can include any suitable configurations according to examplesof the disclosure. It is to be understood that the display nodes used toform the touch nodes are not limited to those described above, but canbe any suitable size or shape to permit touch capabilities according toexamples of the disclosure.

FIG. 5 is a three-dimensional illustration of an exploded view (expandedin the z-direction) of example display node stackups 500 showing some ofthe elements within the node stackups of an example integrated touchscreen 550. Stackups 500 can include a configuration of conductive linesthat can be used to group common electrodes, such as common electrodes401, into drive region segments and sense regions, such as shown in FIG.4, and to link drive region segments to form drive lines.

Stackups 500 can include elements in a first metal (M1) layer 501, asecond metal (M2) layer 503, a common electrode (Vcom) layer 505, and athird metal (M3) layer 507. Each display node can include a commonelectrode 509, such as common electrodes 401 in FIG. 4 that is formed inVcom layer 505. M3 layer 507 can include connection element 511 that canelectrically connect together common electrodes 509. In some displaynodes, breaks 513 can be included in connection element 511 to separatedifferent groups of common electrodes 509 to form drive region segments515 and a sense region 517, such as drive region segments 403 and senseregion 405, respectively. Breaks 513 can include breaks in thex-direction that can separate drive region segments 515 from senseregion 517, and breaks in the y-direction that can separate one driveregion segment 515 from another drive region segment. M1 layer 501 caninclude tunnel lines 519 that can electrically connect together driveregion segments 515 through connections, such as conductive vias 521,which can electrically connect tunnel line 519 to the grouped commonelectrodes in drive region segment display nodes. Tunnel line 519 canrun through the display nodes in sense region 517 with no connections tothe grouped common electrodes in the sense region, e.g., no vias 521 inthe sense region. The M1 layer can also include gate lines 520. M2 layer503 can include data lines 523. Only one gate line 520 and one data line523 are shown for the sake of clarity; however, a touch screen caninclude a gate line running through each horizontal row of display nodesand multiple data lines running through each vertical row of displaynodes, for example, one data line for each red, green, blue (RGB) colorsub-node in each node in a vertical row of an RGB display integratedtouch screen.

Structures such as connection elements 511, tunnel lines 519, andconductive vias 521 can operate as a touch sensing circuitry of a touchsensing system to detect touch during a touch sensing phase of the touchscreen. Structures such as data lines 523, along with other node stackupelements such as transistors, pixel electrodes, common voltage lines,data lines, etc. (not shown), can operate as display circuitry of adisplay system to display an image on the touch screen during a displayphase. Structures such as common electrodes 509 can operate asmultifunction circuit elements that can operate as part of both thetouch sensing system and the display system.

For example, in operation during a touch sensing phase, gate lines 520can be held to a fixed voltage while stimulation signals can betransmitted through a row of drive region segments 515 connected bytunnel lines 519 and conductive vias 521 to form electric fields betweenthe stimulated drive region segments and sense region 517 to createtouch nodes, such as touch node 226 in FIG. 2. In this way, the row ofconnected together drive region segments 515 can operate as a driveline, such as drive line 222, and sense region 517 can operate as asense line, such as sense line 223. When an object such as a fingerapproaches or touches a touch node, the object can affect the electricfields extending between the drive region segments 515 and the senseregion 517, thereby reducing the amount of charge capacitively coupledto the sense region. This reduction in charge can be sensed by a sensechannel of a touch sensing controller connected to the touch screen,such as touch controller 206 shown in FIG. 2, and stored in a memoryalong with similar information of other touch nodes to create an “image”of touch.

A touch sensing operation according to examples of the disclosure willbe described with reference to FIG. 6. FIG. 6 shows partial circuitdiagrams of some of the touch sensing circuitry within display nodes ina drive region segment 601 and a sense region 603 of an example touchscreen according to examples of the disclosure. For the sake of clarity,only one drive region segment is shown. Also for the sake of clarity,FIG. 6 includes circuit elements illustrated with dashed lines tosignify some circuit elements operate primarily as part of the displaycircuitry and not the touch sensing circuitry. In addition, a touchsensing operation is described primarily in terms of a single displaynode 601 a of drive region segment 601 and a single display node 603 aof sense region 603. However, it is understood that other display nodesin drive region segment 601 can include the same touch sensing circuitryas described below for display node 601 a, and the other display nodesin sense region 603 can include the same touch sensing circuitry asdescribed below for display node 603 a. Thus, the description of theoperation of display node 601 a and display node 603 a can be consideredas a description of the operation of drive region segment 601 and senseregion 603, respectively.

Referring to FIG. 6, drive region segment 601 includes a plurality ofdisplay nodes including display node 601 a. Display node 601 a caninclude a TFT 607, a gate line 611, a data line 613, a pixel electrode615, and a common electrode 617. FIG. 6 shows common electrode 617connected to the common electrodes in other display nodes in driveregion segment 601 through a connection element 619 within the displaynodes of drive region segment 601 that is used for touch sensing asdescribed in more detail below. Sense region 603 includes a plurality ofdisplay nodes including display node 603 a. Display node 603 a includesa TFT 609, a data line 614, a pixel electrode 616, and a commonelectrode 618. TFT 609 can be connected to the same gate line 611 as TFT607. FIG. 6 shows common electrode 618 connected to the commonelectrodes in other display nodes in sense region 603 through aconnection element 620 that can be connected, for example, in a borderregion of the touch screen to form an element within the display nodesof sense region 603 that is used for touch sensing as described in moredetail below.

During a touch sensing phase, gate line 611 can be connected to a powersupply, such as a charge pump, that can apply a voltage to maintain TFTs609 in the “off” state. Drive signals can be applied to commonelectrodes 617 through a tunnel line 621 that is electrically connectedto a portion of connection element 619 within a display node 601 b ofdrive region segment 601. The drive signals, which are transmitted toall common electrodes 617 of the display nodes in drive region segment601 through connection element 619, can generate an electrical field 623between the common electrodes of the drive region segment and commonelectrodes 618 of sense region 603, which can be connected to a senseamplifier, such as a charge amplifier 626. Electrical charge can beinjected into the structure of connected common electrodes of senseregion 603, and charge amplifier 626 converts the injected charge into avoltage that can be measured. The amount of charge injected, andconsequently the measured voltage, can depend on the proximity of atouch object, such as a finger 627, to the drive and sense regions. Inthis way, the measured voltage can provide an indication of touch on ornear the touch screen.

Referring again to FIG. 5, it can be seen from FIG. 5 that some displaynodes of touch screen 550 include different elements than other displaynodes. For example, a display node 551 can include a portion ofconnection element 511 that has breaks 513 in the x-direction and they-direction, and display node 551 does not include tunnel line 519. Adisplay node 553 can include a portion of connection element 511 thathas a break 513 in the x-direction, but not in the y-direction, and caninclude a portion of tunnel line 519 and a via 521. Other display nodescan include other differences in the configuration of stackup elementsincluding, for example, no breaks 513 in connection element 511, aportion of tunnel line 519 without a via 521, etc.

The proximity of various circuit elements of integrated touch screens,such as touch screen 550, can result in coupling of signals betweendifferent systems of the touch screen. For example, noise that isgenerated by power systems, such as a gate line system that appliesvoltage to gate lines of the touch screen during a touch sensing phase,can be coupled into the touch sensing system, which can potentiallycorrupt touch sensing signals. Proximal electronics can work to corrupttouch sensing signals by presenting parasitic capacitive pathways thatdistort the measurement of the change in capacitance between the drivelines and the sense lines which are indicative of a touch on the touchpanel.

FIG. 7a illustrates an example touch sensing circuit according toexamples of the disclosure. As illustrated, touch sensing circuit 700can include a drive line 706 that can be stimulated by a stimulationvoltage source 702. Sense line 708 can be located proximally to driveline 706 such that charge on the drive line provided by stimulationvoltage source 702 can be partially coupled via capacitive pathway 704onto sense line 708. As discussed above, the amount of charge coupledonto the sense line 708 from drive line 706 can vary depending on theproximity of a finger or an object to the crossing of the drive line andsense line. The charge coupled onto the sense line can then be detectedby sense circuitry 710, which can detect the changes in the mutualcapacitance 704 between drive line 706 and sense line 708. The signalreceived by the detection circuitry can be characterized by equation 1below:(s*C _(o))/(1+τ₁ *s)  (1)wherein s represents the complex frequency, C_(o) represents the mutualcapacitance between the drive line 706 and sense line 708, and τ₁represents the RC time constant of the circuit.

FIG. 7b illustrates an example touch sensing circuit with parasiticcapacitive pathways according to examples of the disclosure. Asdiscussed above, the proximity of various electronics to touch detectionhardware can create parasitic pathways that can work to distort theability of the detection circuit 710 to accurately measure the change incapacitances associated with a finger or object touching or in closeproximity to the device. FIG. 7b illustrates an example touch sensingcircuit with parasitic capacitive pathways created by proximal gatelines. While parasitic capacitive pathways created by gate lines areshown for purposes of illustration, one skilled in the art wouldrecognize that the disclosure is not so limiting and the conceptsdescribed below could be applied to parasitic capacitive pathwayscreated by other electronics proximal to the touch sensing hardware,such as power circuitry or other display circuitry. As illustrated inFIG. 7b , the touch circuit described in FIG. 7a can contain parasiticcapacitive pathways that are created by the proximity of a gate line716. As illustrated, two such pathways can be created: the first,depicted by capacitor 712, can represent the mutual capacitance betweenthe drive line 706 and the gate line 716. The second pathway, depictedby capacitor 714, can represent the mutual capacitance between the senseline 708 and the gate line 716.

When a stimulation signal is applied by the stimulation voltage source702 to drive line 706, the parasitic capacitive pathways can createalternate ways for charge to be coupled onto the sense lines. Asillustrated, the first pathway 722 can represent the mutual capacitancebetween the drive line 706 and the sense line 708 described above andcharacterized by equation (1) above. A second pathway 724 can be createdvia the mutual capacitance 712 between the drive line 706 and gate line716, and the mutual capacitance 714 between the gate line 716 and thesense line 708. Charge from the stimulation voltage source 702 can becoupled to the gate line and from the gate line to the sense line. Thisseries of couplings can thus couple a second signal onto sense line 708for detection by the detection circuit 710. The signal created by thesecond pathway 724 can be characterized by the following equation:(s ² *R _(g) *C ₁ *C ₂)/(1+τ₂ *s)  (2)wherein R_(g) represents the effective resistance of the gate line(discussed in further detail below), C₁ represents the mutualcapacitance between the drive line 706 and the gate line 716, C₂represents the mutual capacitance between the sense line 708 and thegate line 716, and τ₂ represents the RC time constant of the pathway724. τ₂ can be represented by the equation:R _(g)*(C ₁ +C ₂ +C ₃)  (3)wherein C₃ represents the effective capacitance of the gate line 716.The effective capacitance of the gate line 716 can be an amalgamation ofvarious capacitances created by display electronics such as the datalines, pixel electrodes and common electrodes discussed above. Theeffective resistance of the gate line R_(g) can be a product of themetal used to create the gate lines.

Equation 4 below can represent the effective signal seen by detectioncircuitry 710, which is the combination of the signals from bothpathways:(s*C _(o))/(1+τ₁ *s)+(s ² *R _(g) *C ₁ *C ₂)/(1+τ₂ *s)  (4)

FIG. 8 illustrates an example touch sensing detection and demodulationcircuit according to examples of the disclosure. The detection circuitry710 illustrated in FIGS. 7a and 7b can be implemented in a number ofways, including the circuit 800 depicted in FIG. 8. As illustrated,detection circuit 800 can include an analog front end (AFE) 802 that caninclude an operational amplifier 804 with feedback capacitor 806. TheAFE can receive signals from the sense line 708 and can provide signalbuffering and other pre-processing functions such as filtering prior todemodulation. Detection and demodulation circuit 800 can also contain ademodulator 814 that demodulates the signal and then filters it tospectrally isolate the desired data. Demodulator 814 can contain a mixer808 that receives the output of the AFE 802 and a signal from a localoscillator (LO) 810 at its inputs. The output of the AFE 802 can behomodyned with the signal provided by LO 810 and the output of the mixer808 can then be filtered and sent to a processor for further processing.In a homodyned demodulation architecture, the frequency and phase of theLO can be tuned to the frequency and phase of the signal appearing atthe output of the AFE 802 in order to maximize the magnitude of thedetected signal after detection. However, due to the parasiticcapacitance pathways discussed above in reference to FIG. 7b , twosignals can appear at the output of the AFE 802, the first signalcorresponding to the mutual capacitance between the drive and senselines that is the desired signal to be detected, and a second signalcreated by the parasitic pathways described above that can act as noiseto the desired signal. Due to the presence of these two signals, tuningthe phase of the LO can present an opportunity to maximize the magnitudeof desired signal while at the same time minimizing the magnitude of thenoise signal.

FIGS. 9A-9C illustrate various relationships between the phase of asignal and the phase of a local oscillator. The vector diagrams of FIG.9a-c can help to illustrate the relationship between a signal phase andthe LO phase, and the resultant signal that can be produced by a mixer,given the phase relationship between the signal and the LO. Forinstance, in FIG. 9a , the signal can be represented by a vector S inwhich the magnitude of the vector is expressed as a length of the vectorand the phase of the vector can be expressed as an angle of incidencewith x-axis of the vector diagram. The x-axis of the diagram can be madeparallel to the phase of the LO, such that any angle of incidencebetween the vector S and the x-axis can be indicative of the phasediscrepancy between the signal and the LO. In FIG. 9a , the vector S hasan angle of incidence of θ with the x-axis, thus being indicative of aphase discrepancy of θ° between the signal and the LO. The vector S canbe resolved into 2 components, one that is parallel to the x-axis, andone that is orthogonal to the x-axis, i.e. the y-axis. As known to oneskilled in the art, it is the component of the vector that is parallelto the x-axis that appears on the output of the mixer, while thecomponent of the vector that is orthogonal to the x-axis does not appearat the output of the mixer and is cancelled out via destructiveinterference. Thus, turning back to FIG. 9a , the vector S can beresolved into x and y components S_(x) and S_(y), respectively, whereinS_(x) can appear at the output of the mixer, after having mixed the LOwith the signal S, and S_(y) can be cancelled out via destructiveinterference. The resultant vector S_(x) can thus appear at the outputof the mixer; however, its magnitude can be diminished by an amountequivalent to the magnitude of the orthogonal component of the signalS_(y) that was cancelled out.

FIG. 9b can illustrate the example in which the LO is tuned to match thephase of the signal S. In such an example the angle of incidence θ tothe x-axis can be θ°. Therefore, when vector S is resolved into its xand y components, the x component S_(x) can be equal to the magnitude ofthe original vector S and the y component S_(y) is zero. Thus, the LOcan be tuned such that the phase can be matched to the signal S, and theoutput of the mixer can be maximized. FIG. 9c can illustrate the examplein which the LO can be tuned to be orthogonal to the phase of the signalS. In such an example the angle of incidence θ to the x-axis can be 90°.Therefore, when vector S is resolved into its x and y components, the xcomponent S_(x) can be zero, while the y component can be equal to themagnitude of the vector S. However, since the y component can representthe portion of the signal that is destructively interfered with, theoutput of the mixer can be approximately 0 since there is no x componentto the vector S.

FIGS. 10A-10C illustrate various relationships between the phase of asignal, the phase of a noise signal, and the phase of a local oscillatoraccording to examples of the disclosure. As discussed above, theparasitic capacitance pathway created by proximal electronics can act asa noise signal during touch detection. FIGS. 10a-10c can illustratevarious phase relationships between the touch signal S, the parasiticcapacitance signal N and the LO of the demodulator. FIG. 10a illustratesan example relationship in which both a noise signal N and a touchsignal S can be out of phase with the LO. As illustrated, signal S andsignal N can be resolved into their x and y components. As discussedabove, the x components can be produced at the output of a mixer whilethe y components can be cancelled out. Therefore when both signals S andN are present, the mixer can output N_(x) and S_(x) while N_(y) andS_(y) can be cancelled out. The presence of N_(x) along with S_(x) atthe output of the mixer can lead to a diminished signal to noise ratioduring touch detection. A diminished signal to noise ratio can lead atouch input device to detect false touches, i.e. detecting a touch whenno touch is actually present, or failing to detect touch input eventsthat have occurred on the device.

FIG. 10b illustrates the relationship of phase between the noise signal,the touch signal and the LO, when the LO is tuned to match the phase ofthe touch signal. The magnitude of the touch signal as seen at theoutput of the mixer can equal S_(x) as the touch signal would no longerhave an orthogonal component relative to the phase of the LO. By tuningthe LO phase to match the phase of the touch signal, the magnitude ofthe touch signal seen on the output of the mixer can be maximized.However, since the LO is not tuned to the noise signal, the noise vectorN can have a horizontal/in-phase component N_(x) and avertical/orthogonal component N_(y). As discussed above, thehorizontal/in-phase component N_(x) may be produced at the output of themixer while the vertical/orthogonal component may be cancelled out.Since the N_(y) component of the noise signal N may be cancelled out bythe mixer, the magnitude of the noise signal appearing at the output ofthe mixer may be reduced as compared to the original signal pre-mixer.Therefore, when the LO is tuned to match the phase of the touch signal,the touch signal can see its magnitude maximized while the noise signalis diminished due to its orthogonal component being destructivelyinterfered with. Nonetheless, the signal-to-noise ratio can bediminished by the presence of noise created by parasitic pathways evenwhen the LO is tuned to match the phase of the touch signal.

FIG. 10c illustrates the relationship of phase between the noise signal,the touch signal and the LO, when the LO is tuned to be orthogonal tothe phase of the noise signal. As illustrated, by tuning the LO to beorthogonal (i.e., 90° out of phase) to the noise signal, the noisesignal vector N will not have an in-phase/horizontal component, in otherwords Nx=0. Thus the output of the mixer can be free of any noise signalcomponent. However, as illustrated, the touch signal S can suffer adegradation at the output of the mixer, since the orthogonal componentof the touch signal Sy can be cancelled out by destructive interferencewith the LO signal. Nonetheless, by tuning the LO phase to be orthogonalto the noise signal, thus effectively cancelling out the noise throughdestructive interference, the signal to noise ratio at the output of themixer can be maximized.

The phase of the LO can be tuned at the time of manufacture of thedevice. The LO can be tuned when no touch signal is present so as toensure that the LO is being tuned to the noise signal only. When theoutput of the mixer is minimized in response to the tuned LO phase, thephase calibration process can be terminated. While the phase of the LOcan be tuned to be orthogonal to the noise signal at the time ofmanufacture, the noise signal can dynamically change phase duringoperation of the device.

For example, as discussed above, circuitry associated with the displaycan create parasitic capacitive pathways on the touch detectioncircuitry. The parasitic capacitive pathways and their coupling behaviorwith the touch detection circuitry can be affected by the signals beingtransmitted at any particular time by the display circuitry. Forexample, if a particular area of the display is displaying a brightcolor then the parasitic capacitance imparted to the touch detectioncircuit can be different in terms of phase and magnitude than if thecolor were dull. In another example, exposure of the device to hot andcold environments can change the resistivity of the metal that makes upthe proximal electronics. As discussed above, the noise signal candepend on the resistivity of the metal and thus the temperature of thedevice can change the phase of the noise signal. In other examples, thephase of the noise signal can be affected by the age of the device, andcertain parameters of the display electronics such as resistivity andcapacitance can change over time. Due to the dynamic nature of theparasitic capacitance experienced by the touch detection circuitry, thephase of the LO may at times no longer be orthogonal to the phase of thenoise. As discussed above, a lack of orthogonality can result indegradation to the signal to noise ratio of the touch detection circuit.While it has been empirically determined that the changes to the phaseof the noise signal in response to the dynamic changes in parasiticcapacitance can be small, nonetheless any loss of orthogonality betweenthe noise signal phase and the LO phase can result in a significantdegradation to SNR.

FIG. 11 illustrates an example method of dynamically adjusting a localoscillator phase according to examples of the disclosure. At a firststep S1100 the magnitude of the measured signal at the output of thetouch detection circuit can be measured. The method then can move tostep 1102 in which the resistivity of the gate line can be dithered, orin other words temporarily changed and then reverted back to itsoriginal state. A more detailed discussion of dithering can be foundbelow. The method can then move to step 1104 where the magnitude of thesignal is measured again and a change in the magnitude of the signal asa result of the dithering of the resistivity can be determined. Themethod can then move to step 1106 where the determined change inmagnitude can be compared against a pre-determined threshold.

Due to the sinusoidal nature of the signals involved touch detection, ifthe LO is tuned to be orthogonal to noise signal or approximatelyorthogonal, then the dithering of the resistivity of the gate line cancause a change in magnitude of the noise signal that is less than thechange in magnitude of the noise signal had the LO not been tuned to beorthogonal to the noise signal. Therefore a pre-determined threshold canbe established such that based on the change in magnitude of the noisesignal caused by the dithering, the device can determine whether the LOis approximately tuned to be orthogonal to the noise signal or if the LOphase should be adjusted. Thus at step 1106 if the change in magnitudeis found to be less than the pre-determined threshold then the methodcan move to step 1108 and the LO tuning method can be terminated. If thechange in magnitude is above a pre-determined threshold, than the methodcan move to step 1110 where the LO phase is adjusted by a pre-determinedamount and the process is repeated.

In order to illustrate methods of dithering the resistance of the gatelines, the structure of the gate lines can be examined in order toidentify areas in which the resistance can be changed to produce thedithering effect. FIG. 12 illustrates an example gate line voltagesystem according to examples of the disclosure. Gate line voltage system1200 can consist of gate lines 1208, each row of the display having itsown gate line. The gate lines 1208 can be connected at its ends to atail TFT (thin film transistor) 1202, for the purpose of selectivelyturning on and off a gate line at a given time. Each tail TFT 1202 canbe connected to a voltage gate line (VGL) unit 1210 whose purpose can beto provide varying voltages to each individual gate line. VGL unit 1210can be connected to reservoir capacitor 1204. Reservoir capacitor 1204can be connected to the VGL unit 1210 to allow the gate lines tomaintain their voltage during time periods in-between refreshing therows of the display. The gate lines 1208, tail TFTs 1202, VGL units 1210and reservoir capacitors can all contribute to the effective resistanceof the gate line.

FIG. 13 illustrates an example method of dithering the resistance of agate line voltage system. For purposes of illustration the circuit ofFIG. 12 has been simplified to illustrate only one row of the gate linevoltage system. As described in reference to FIG. 12, gate line 1308 canbe connected to tail TFT 1302. Tail TFT 1302 can be connected toreservoir capacitor 1306 via VGL trace 1304. As shown in FIG. 12, thereservoir capacitor 1204 can be connected to ground or another referencevoltage. In the example of FIG. 13, the reservoir capacitor 1306 can beconnected to a network of paths to ground. Each path can have differingresistances and can be selectively activated and deactivated usingtransistors. For instance, path 1320 can include a transistor 1310 thatcan selectively connect the reservoir capacitor 1306 to ground. Path1322 can include resistor 1312 and transistor 1316. When path 1320 isactivated via transistor 1316, the gate line voltage system can have aneffective resistance R1. If path 1320 is deactivated and path 1322 isactivated, due to the resistor 1312, path 2 can change the effectiveresistance of the gate line voltage system to R2. R1 and R2 can bedifferent values. By selectively activating path 1320 and 1322, thedevice can control the value of the effective resistance of the gateline voltage system, and thus it can effectively dither the resistanceof the gate line according to the description in FIG. 11. Multiplepathways can be created, with each path imparting a different resistanceon the gate line voltage system. For instance, path 1324 can have aresistor 1314 whose resistance differs from the resistor 1312 of path1322. Paths 1320, 1322 and 1324 can be selectively activated anddeactivated in different combinations to produce different gate lineresistances as desired by the device in order to effectively dither theresistance of the gate line.

FIG. 14 illustrates another example method of dithering the resistanceof a gate line voltage system. Reservoir capacitor 1306 can be connectedto ground via pathway 1402 that goes through resistors 1406 and 1408.Transistors 1310 and 1410 can be used to create alternative pathways toconnect reservoir capacitor 1306 to ground. For instance, whentransistor 1310 is activated, reservoir capacitor 1306 can be connectedto ground directly, thus bypassing resistors 1406 and 1408. Whentransistor 1310 is deactivated and transistor 1410 is activated,reservoir capacitor 1306 can be connected to ground via resistor 1408while bypassing resistor 1406. In this way, by selectively activatingand deactivating transistors 1310 and 1410, three separate paths toground can be created for reservoir capacitor 1306, each path carrying adifferent effective resistance, thus changing the overall resistance ofthe voltage gate line system.

FIG. 15 illustrates another example method of dithering the resistanceof a gate line voltage system. In this example, alternate paths betweenthe gate line 1512 and the reservoir capacitor 1506 can be created, witheach path imparting a different resistance on the gate line, thuschanging the effective gate line resistance seen by the touch detectionsystem. In the example of FIG. 15, two separate tail TFTs 1502 and 1504can be connected to an individual gate line 1512. When tail TFT 1502 isactivated it creates path 1506 between gate line 1512 and reservoircapacitor 1506. When tail TFT 1504 is activated, it can create path 1508between gate 1512 and reservoir capacitor 1506. Tail TFT 1504 can belarger than tail TFT 1502. By choosing tail TFT 1504 to be larger thantail TFT 1502, when tail TFT 1504 is activated, the effective resistancepath differs from the effective resistance of path 1506, thus creatingthe dithering effect as described above.

The choice of dithering the tail TFT paths as illustrated in FIG. 15versus dithering the grounding paths for the reservoir capacitor asillustrated in FIGS. 13 and 14 can provide certain advantages anddisadvantages. For instance while dithering the reservoir capacitor pathcan be less complex than dithering the tail TFTs (there is one tail TFTfor every row of the display, whereas there is only two reservoircapacitors for the display), the effective gate line resistance seen atevery row can be changed, meaning that control of the gate lineresistance is done at the display level rather than at the row level. Incontrast, by dithering the each tail TFT path, the control of theeffective gate line resistance can be localized to each individual row.This may be advantageous if each LO in the touch detection circuit isused for only one localized area of the display, thus providing a moreprecise tuning to the LO at each localized area of the display.

The change in magnitude caused by dithering can be measured in manydifferent ways. In one example, a touch image can be obtained while theeffective resistance of the gate line is held at a particular value.After the image is obtained, the effective resistance of the gate linecan be changed and another touch image obtained. The change in magnitudebetween the two touch images can be compared to determine the change inmagnitude. In another example, the process above can be repeated overmany touch images, and the magnitude of each touch image can beintegrated over time to determine the change in magnitude. In this way,any changes in magnitude caused by other noise sources or variations dueto system conditions can be integrated out, thus ensuring that thechange in magnitude detected is caused by the dithering.

In the above example, the change in magnitude due to dithering can bedetermined only after multiple touch images have been obtained. This canmean that the LO phase can lose orthogonality and then regainorthogonality only after multiple touch images have been rendered. Inother examples the change in magnitude due to dithering can bedetermined during one touch image by dithering the effective resistanceof the gate line at a fixed frequency. For example, by dithering thegate resistance at a fixed frequency that is different from thestimulation frequency of the touch signal, the change in magnitude ofthe touch signal caused by the dithering can be spectrally separatedfrom the touch signal. As discussed above with respect to equations 1-4,the touch signal and the noise signal can appear at the same frequencybased on the stimulation signal provided to the touch detection section.By dithering the gate line resistance at a fixed frequency, the changein magnitude of the noise signal caused by the dithering can bespectrally isolated.

FIG. 16 illustrates an example frequency response of a detected touchand noise signal according to examples of the disclosure. Asillustrated, signal 1604 can represent the touch signal that ismodulated at a frequency F_(stim). For purposes of illustration, Fstimis shown as being 100 KHz. If the effective gate line resistance ismodulated at a frequency of 40 KHz than signals that are representativeof the change in magnitude of the noise signal due to dithering canappear at 140 KHz (signal 1606) and at 60 KHz (signal 1602) on thefrequency spectrum. Since the magnitude of signals 1602 and 1606 aredependent on the change in magnitude due to dithering, they can be usedto determine the orthogonality of the LO phase to the noise phase asdiscussed above.

FIG. 17 shows an exemplary embodiment of an in-cell touch controllerwith additional features for DTX compensation. A transmit channel 1702can generate signals VDTX from FDTX generator 1704 and VSTM from FSTMgenerator 1706. VDTX can have the frequency of the gate line impedancedithering signal and VSTM can be the touch stimulus frequency FSTM whichis used to detect touch inputs. As VSTM passes through the touch pixel1708 it can pass through CSIG which can represent the mutual capacitancebetween a drive line and sense line as described above. VSTM can alsopass through the DTX path described in FIG. 7 that flows through C1, C2,RG and CG. Because C1 and C2 can vary as a function of the pixel voltagelevels, their value can be dependent on the image being produced by thedisplay. Therefore, signal ISNS 1710 into the sense amplifier 1712 of RXanalog front end 1714 can have two components, one being ISIG thecomponent of the signal created by VSTM the other IDTX which can be thecomponent created by VDTX, the latter being image dependent. Ditheringof the gate line impedance at FDTX can cause the IDTX component to bemixed with the stimulus of frequency FSTM passing through the DTXnetwork. Therefore the frequency of IDTX can have a frequencyFSTM+/−FDTX, as shown in FIG. 16

The RX analog front end 1714 can convert, filter and digitize thissignal for further processing by a digital subsystem 1716. Twodemodulation paths can be provided. The primary demodulation path candemodulate the touch signal at frequency FSTM, the secondarydemodulation path can demodulate the DTX component at FSTM+/−FDTX. Thesecondary demodulation path can use an I/Q vector demodulator know inthe art, in order to calculate the magnitude of the DTX signal. Thein-cell touch controller 1718 can post the touch and DTX magnitude intouch image memory 1720 and DTX magnitude memory 1722, respectively.Either a processor and/or correction logic 1724 can adjust the phase ofthe signal into the primary demodulation path based on the DTX magnitudeas to minimize the DTX component, as outlined in FIGS. 10 and 11.Similarly, processor and/or correction logic 1724 can apply correctionto the touch data before and/or after a touch scan completes. Applyingcorrection can involve addition, subtraction, division or multiplicationof correction factors during touch scanning and/or after touch scanningcompletes.

Therefore, according to the above, some examples of the disclosure aredirected to a touch input device configured to reduce the effects ofnoise, the touch input device comprising a plurality of signalgenerators, at least one of the plurality of signal generatorsconfigured to generate a first stimulation signal and at least one ofthe plurality of signal generators configured to generate a secondstimulation signal, a plurality of first circuit elements configured todetect a touch input on the touch input device, a plurality of secondcircuit elements, the plurality of second circuit elements locatedproximal to the plurality of second circuit elements, and a processorcapable of driving the first circuit elements with the first stimulationsignal, measuring a detected touch signal, driving the second circuitelements with the second stimulation signal, measuring a change in thedetected touch signal caused by the dithering, comparing the change to apre-determined threshold, and adjusting a demodulation phase if thechange in touch signal is above the pre-determined threshold.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, driving the second circuit elements with thesecond stimulation signal includes dithering a parameter of theplurality of second circuit elements. Additionally or alternatively toone or more of the examples disclosed above, in some examples, ditheringa parameter of the plurality of second circuit elements further includesdithering an effective resistance of the circuit element. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, the plurality of second circuit elements include a gate lineof a display. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, dithering the effectiveresistance of a gate line includes dithering a resistance associatedwith a reservoir capacitor of the gate line. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, dithering the effective resistance of a gate line includesdithering a resistance associated with a tail TFT of the gate line.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the processor is further caused to correct atouch image of the touch input device based on the measured change inthe in the detected touch signal caused by the dithering. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, the first stimulation signal and the second stimulation signalare independently adjustable.

Some examples of the disclosure are directed to a method of dynamicallyreducing the effect of noise on a touch sensor panel, the methodcomprising measuring a detected touch signal, dithering a parameter of acircuit element proximal to the touch sensor panel, measuring a changein the detected touch signal caused by the dithering, comparing thechange to a pre-determined threshold, adjusting a demodulation phase ifthe change in touch signal is above the pre-determined threshold, andcorrecting the measured touch signal if the change in touch signal isabove the pre-determined threshold. Additionally or alternatively to oneor more of the examples disclosed above, in some examples, dithering aparameter of a circuit element proximal to the touch sensor panelincludes dithering an effective resistance of the circuit element.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the circuit element includes a gate line of adisplay. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, dithering the effective resistance ofa gate line includes dithering a resistance associated with a reservoircapacitor of the gate line. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, dithering theeffective resistance of a gate line includes dithering a resistanceassociated with a tail TFT of the gate line. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, measuring a change in the detected touch signal caused by thedithering includes dithering the parameter over a plurality of touchimages, and comparing the plurality of touch images to determine thechange. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, measuring a change in the detectedtouch signal caused by the dithering includes dithering the parameter ata fixed frequency during an acquisition of a touch image, acquiring atouch image, and filtering the acquired touch image so as to isolate aportion of the acquired touch image correlated to the dithering of theparameter. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the demodulation phase is adjustedsuch that the phase is orthogonal to a phase of the cross-talk noise.

Some examples of the disclosure are directed to a non-transitorycomputer readable storage medium having stored thereon a set ofinstructions for reducing the effects of noise in a touch sensor panel,that when executed by a processor causes the processor to measure adetected touch signal, dither a parameter of a circuit element proximalto the touch sensor panel, measure a change in the detected touch signalcaused by the dithering, compare the change to a pre-determinedthreshold, adjust a demodulation phase if the change is above thepre-determined threshold, correct the measured touch signal if thechange in the in the touch signal is above the pre-determined threshold.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, dithering a parameter of a circuit elementproximal to the touch sensor panel includes dithering an effectiveresistance of the circuit element. Additionally or alternatively to oneor more of the examples disclosed above, in some examples, the circuitelement includes a gate line of a display. Additionally or alternativelyto one or more of the examples disclosed above, in some examples,dithering the effective resistance of a gate line includes dithering aresistance associated with a reservoir capacitor of the gate line.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, dithering the effective resistance of a gateline includes dithering a resistance associated with a tail TFT of thegate line. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, measuring a change in the detectedtouch signal caused by the dithering includes dithering the parameterover a plurality of touch images, and comparing the plurality of touchimages to determine the change in the touch signal. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, measuring a change in the detected touch signal caused by thedithering includes dithering the parameter at a fixed frequency duringan acquisition of a touch image, acquiring a touch image, and filteringthe touch image so as to isolate a portion of the acquired touch imagecorrelated to the dithering of the parameter. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the phase of the local oscillator is adjusted such that thephase is orthogonal to a phase of the cross-talk noise.

Some examples of the disclosure are directed to a method of dynamicallyreducing the effect of noise on a touch sensor panel, the methodcomprising measuring a detected touch signal, dithering a parameter of acircuit element proximal to the touch sensor panel, measuring a changein the detected touch signal caused by the dithering, comparing thechange to a pre-determined threshold, and adjusting a demodulation phaseif the change in touch signal is above the pre-determined threshold.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, dithering a parameter of a circuit elementproximal to the touch sensor panel includes dithering an effectiveresistance of the circuit element. Additionally or alternatively to oneor more of the examples disclosed above, in some examples, the circuitelement includes a gate line of a display. Additionally or alternativelyto one or more of the examples disclosed above, in some examples,dithering the effective resistance of a gate line includes dithering aresistance associated with a reservoir capacitor of the gate line.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, dithering the effective resistance of a gateline includes dithering a resistance associated with a tail TFT of thegate line. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, measuring a change in the detectedtouch signal caused by the dithering includes dithering the parameterover a plurality of touch images, and comparing the plurality of touchimages to determine the change. Additionally or alternatively to one ormore of the examples disclosed above, in some examples, measuring achange in the detected touch signal caused by the dithering includesdithering the parameter at a fixed frequency during an acquisition of atouch image, acquiring a touch image, and filtering the acquired touchimage so as to isolate a portion of the acquired touch image correlatedto the dithering of the parameter. Additionally or alternatively to oneor more of the examples disclosed above, in some examples, thedemodulation phase is adjusted such that the phase is orthogonal to aphase of the cross-talk noise.

Some examples of the disclosure are directed to a touch input deviceconfigured to reduce the effects of noise, the touch input devicecomprising a processor capable of measuring a detected touch signal,dithering a parameter of a circuit element proximal to the touch sensorpanel, measuring a change in the detected touch signal caused by thedithering, comparing the change to a pre-determined threshold, andadjusting a demodulation phase if the change in touch signal is abovethe pre-determined threshold. Additionally or alternatively to one ormore of the examples disclosed above, in some examples, dithering theparameter of the circuit element proximal to the touch sensor panelincludes dithering an effective resistance of the circuit element.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the circuit element includes a gate line of adisplay. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, dithering the effective resistance ofa gate line includes dithering a resistance associated with a reservoircapacitor of the gate line. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, dithering theeffective resistance of a gate line includes dithering a resistanceassociated with a tail TFT of the gate line. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, measuring a change in the detected touch signal caused by thedithering includes dithering the parameter over a plurality of touchimages, and comparing the plurality of touch images to determine thechange in the touch signal. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, measuring a change inthe detected touch signal caused by the dithering includes dithering theparameter at a fixed frequency during an acquisition of a touch image,acquiring a touch image, and filtering the touch image so as to isolatea portion of the acquired touch image correlated to the dithering of theparameter. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the demodulation phase is adjustedsuch that the phase is orthogonal to a phase of the cross-talk noise.

Some examples of the disclosure are directed to a non-transitorycomputer readable storage medium having stored thereon a set ofinstructions for reducing the effects of noise in a touch sensor panel,that when executed by a processor causes the processor to measure adetected touch signal, dither a parameter of a circuit element proximalto the touch sensor panel, measure a change in the detected touch signalcaused by the dithering, compare the change to a pre-determinedthreshold, and adjust a demodulation phase if the change is above thepre-determined threshold. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, dithering a parameterof a circuit element proximal to the touch sensor panel includesdithering an effective resistance of the circuit element. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, the circuit element includes a gate line of a display.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, dithering the effective resistance of a gateline includes dithering a resistance associated with a reservoircapacitor of the gate line. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, dithering theeffective resistance of a gate line includes dithering a resistanceassociated with a tail TFT of the gate line. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, measuring a change in the detected touch signal caused by thedithering includes dithering the parameter over a plurality of touchimages, and comparing the plurality of touch images to determine thechange in the touch signal. Additionally or alternatively to one or moreof the examples disclosed above, in some examples, measuring a change inthe detected touch signal caused by the dithering includes dithering theparameter at a fixed frequency during an acquisition of a touch image,acquiring a touch image, and filtering the touch image so as to isolatea portion of the acquired touch image correlated to the dithering of theparameter. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the phase of the local oscillator isadjusted such that the phase is orthogonal to a phase of the cross-talknoise.

Although the disclosed examples have been fully described with referenceto the accompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art. Suchchanges and modifications are to be understood as being included withinthe scope of the disclosed examples as defined by the appended claims.

What is claimed is:
 1. A touch input device configured to reduce effectsof noise, the touch input device comprising: a plurality of signalgenerators, at least one of the plurality of signal generatorsconfigured to generate a first stimulation signal and at least one ofthe plurality of signal generators configured to generate a secondstimulation signal; a plurality of first circuit elements configured todetect a touch input on the touch input device; a plurality of secondcircuit elements, the plurality of second circuit elements locatedproximal to the plurality of first circuit elements; and a processorcapable of: performing a first scan of the touch input devicecomprising: driving the first circuit elements with the firststimulation signal and sensing a first corresponding sense signal; whiledriving the first circuit elements with the first stimulation signal andsensing the first corresponding sense signal, driving the second circuitelements with the second stimulation signal; and adjusting ademodulation phase of a demodulation signal for demodulating the firstcorresponding sense signal; and after the first scan, performing asecond scan of the touch input device comprising: driving the firstcircuit elements with the first stimulation signal and sensing a secondcorresponding sense signal; while driving the first circuit elementswith the first stimulation signal and sensing the second correspondingsense signal, driving the second circuit elements with the secondstimulation signal; and maintaining the demodulation phase of thedemodulation signal for demodulating the second corresponding sensesignal.
 2. The touch input device of claim 1, wherein driving the secondcircuit elements with the second stimulation signal includes dithering aparameter of the plurality of second circuit elements.
 3. The touchinput device of claim 2, wherein dithering the parameter of theplurality of second circuit elements further includes dithering aneffective resistance of the circuit element.
 4. The touch input deviceof claim 3, wherein the plurality of second circuit elements include agate line of a display.
 5. The touch input device of claim 4, whereindithering the effective resistance of the gate line includes dithering aresistance associated with a reservoir capacitor of the gate line. 6.The touch input device of claim 1, wherein the processor is furthercaused to correct a touch image of the touch input device based on achange in the detected touch signal caused by driving the second circuitelements with the second stimulation signal.
 7. The touch input deviceof claim 1, wherein the first stimulation signal and the secondstimulation signal are independently adjustable.
 8. A method ofdynamically reducing the effect of noise on a touch sensor panel, themethod comprising: performing a first scan of the touch sensor panelcomprising: driving first circuit elements configured to detect a touchinput on the touch sensor panel with a first stimulation signal andsensing a first corresponding sense signal on the touch sensor panel;while driving the first circuit elements with the first stimulationsignal and sensing the first corresponding sense signal on the touchsensor panel, driving second circuit elements located proximal to thetouch sensor panel with the second stimulation signal; and adjusting ademodulation phase of a demodulation signal for demodulating the firstcorresponding sense signal; and after the first scan, performing asecond scan of the touch sensor panel comprising: driving the firstcircuit elements with the first stimulation signal and sensing a secondcorresponding sense signal on the touch sensor panel; while driving thefirst circuit elements with the first stimulation signal and sensing thesecond corresponding sense signal on the touch sensor panel, driving thesecond circuit elements with the second stimulation signal; andmaintaining the demodulation phase of the demodulation signal fordemodulating the second corresponding sense signal.
 9. The method ofclaim 8, wherein dithering the parameter of the circuit element proximalto the touch sensor panel includes dithering an effective resistance ofthe circuit element.
 10. The method of claim 9, wherein the circuitelement includes a gate line of a display.
 11. The method of claim 10,wherein dithering the effective resistance of the gate line includesdithering a resistance associated with a reservoir capacitor of the gateline.
 12. The method of claim 10, wherein dithering the effectiveresistance of the gate line includes dithering a resistance associatedwith a tail TFT of the gate line.
 13. The method of claim 8, furthercomprising dithering the parameter over a plurality of touch images, andcomparing the plurality of touch images to determine the change.
 14. Thetouch input device of claim 13, wherein dithering the effectiveresistance of the gate line includes dithering a resistance associatedwith a tail TFT of the gate line.
 15. The method of claim 8, whereinmeasuring a change in the detected touch signal caused by the ditheringincludes: acquiring a touch image; dithering the parameter at a fixedfrequency during the acquisition of the touch image; and filtering theacquired touch image so as to isolate a portion of the acquired touchimage correlated to the dithering of the parameter.
 16. The method ofclaim 8, wherein the demodulation phase is adjusted such that the phaseis orthogonal to a phase of cross-talk noise.
 17. A non-transitorycomputer readable storage medium having stored thereon a set ofinstructions for reducing the effects of noise in a touch sensor panel,that when executed by a processor causes the processor to: perform afirst scan of the touch sensor panel comprising: driving first circuitelements configured to detect a touch input on the touch sensor panelwith a first stimulation signal and sensing a first corresponding sensesignal on the touch sensor panel; while driving the first circuitelements with the first stimulation signal and sensing the firstcorresponding sense signal on the touch sensor panel, driving secondcircuit elements located proximal to the touch sensor panel with thesecond stimulation signal; and adjusting a demodulation phase of ademodulation signal for demodulating the first corresponding sensesignal; and after the first scan, perform a second scan of the touchsensor panel comprising: driving the first circuit elements with thefirst stimulation signal and sensing a second corresponding sense signalon the touch sensor panel; while driving the first circuit elements withthe first stimulation signal and sensing the second corresponding sensesignal on the touch sensor panel, driving the second circuit elementswith the second stimulation signal; and maintaining the demodulationphase of the demodulation signal for demodulating the secondcorresponding sense signal.
 18. The non-transitory computer readablestorage medium of claim 17, wherein dithering the parameter of thecircuit element proximal to the touch sensor panel includes dithering aneffective resistance of the circuit element.
 19. The non-transitorycomputer readable storage medium of claim 18, wherein the circuitelement includes a gate line of a display.
 20. The non-transitorycomputer readable storage medium of claim 19, wherein dithering theeffective resistance of the gate line includes dithering a resistanceassociated with a reservoir capacitor of the gate line.
 21. Thenon-transitory computer readable storage medium of claim 19, whereindithering the effective resistance of the gate line includes dithering aresistance associated with a tail TFT of the gate line.
 22. Thenon-transitory computer readable storage medium of claim 17, furthercomprising dithering the parameter over a plurality of touch images, andcomparing the plurality of touch images to determine the change in thetouch signal.
 23. The non-transitory computer readable storage medium ofclaim 17, wherein measuring the change in the detected touch signalcaused by the dithering includes: acquiring a touch image; dithering theparameter at a fixed frequency during the acquisition of the touchimage; and filtering the touch image so as to isolate a portion of theacquired touch image correlated to the dithering of the parameter. 24.The non-transitory computer readable storage medium of claim 17, whereinthe phase of the demodulation signal is adjusted such that the phase isorthogonal to a phase of cross-talk noise.
 25. A touch input deviceconfigured to reduce effects of noise, the touch input devicecomprising: a plurality of signal generators, at least one of theplurality of signal generators configured to generate a firststimulation signal and at least one of the plurality of signalgenerators configured to generate a second stimulation signal; aplurality of first circuit elements configured to detect a touch inputon the touch input device; a plurality of second circuit elements, theplurality of second circuit elements located proximal to the pluralityof first circuit elements; and a processor capable of: driving the firstcircuit elements with the first stimulation signal; measuring a detectedtouch signal; while measuring the detected touch signal, driving thesecond circuit elements with the second stimulation signal; measuring achange in the detected touch signal caused by driving the second circuitelements with the second stimulation signal; comparing the change in thedetected touch signal to a pre-determined threshold; in accordance witha determination that the change in the detected touch signal is abovethe pre-determined threshold, adjusting a demodulation phase of ademodulation signal for demodulating the detected touch signal; and inaccordance with a determination that the change in the detected touchsignal is below the pre-determined threshold, maintaining thedemodulation phase of the demodulation signal for demodulating thedetected touch signal.